1916] AGRICULTURAL BOTANY. 27 



No concentration of electrolytes with a?:e was observed in these roots. The 

 higher osmotic pressure in older roots is ascribed to increased carbohydrates. 

 In each case the concentration of the total solutes of the sap expressed after 

 freezing was greater than that of sap pressed from the same tissues untreated. 

 The seasonal variations in concentration of the sap obtained by the two methods 

 showed a remarkable similarity. 



Some researches in experimental morphology. — I, On the change of the 

 petiole into a stem by means of grafting, J. L)oyle (Sci. Proc. Roy. Dublin 

 Soc, n. set:, 1^ (1915), No. 33, pp. 405-4U, pis. 7, figs. 3). — This is an account 

 of attempts to ascertain whether the petiole of a plant can be made to function 

 as a stem and to study any accompanying anatomical changes. The plants used 

 were Pelargonium zonale meteor, Solanmn richardi, S. halbesii, San<;hezia 

 nobilis, and Phytolacca dioica. The techuiqiie, progress, and results of the 

 work are describetl. 



It is stated that the petiole, by grafting a sprout upon it, can be made to 

 assume the functions of a stem. The properties of the stem, such as long life 

 duration, indefinitely active cambium, interfascicular cambium linking up 

 bundles, peridermium development, and considerable secondary thickening, all 

 appear in the petiole. It is held that the causes of the secondary thickening lie 

 in the removal of correlational influences, increased mechanical strain, and some 

 influence connected with foliar development, supposedly bound up in some way 

 with the water economy, particularly transpiration. 



A bibliography is appended. 



An investigation of the causes of automatic movements in succulent 

 plants, Edith B. Shkeve (Plant World, IS (1915), Nos. 11, pp. 291-312, figs. 6; 

 12, pp. S31-343, figs. 5). — ^As the result of a study carried out on a number of 

 cacti it is claimed that the seasonal movements observed are correlated with 

 turgidity changes, as were also daily movements which were studied in some 

 detail. Other influences acting in the case of short period movement, through 

 intermediate processes, are temperature, light intensity, evaporative power of 

 the air, and water content of the soil and plant tissue. 



It is claimed that the form of the adult cactus plant and the position of its 

 branches are determined by the water relations existing during the period of 

 growth and secondary thickening of its various parts, and not by any peculiari- 

 ties in its growing point and in its mode of initiating branches. 



The relation of evaporation and soil moisture to plant succession in a 

 ravine, F. T. Ullrich (Bui. III. State Lab. Nat. Hist., 12 (1915), Art. 1, pp. 16, 

 pis. 19). — The author gives an account, with interpretation and discussion of 

 results, of a study during the summer of 1913 on the evaporation rates in differ- 

 ent portions of a ravine which is described. The data obtained are claimed to 

 show clearly that the differences in the rates of evaporation at the various 

 stations are sufficient to indicate that the atmospheric conditions are efl:ective 

 factors in causing plant succession in a ravine. 



A study of the relation of transpiration to the size and number of 

 stomata, W. L. C. Muencher (Amcr. Jour. Bat., 2 (1915), No. 9, pp. 487-50^, 

 figs. 3). — From the determinations made by the methods described upon a num- 

 ber of plants, the author concludes that the number of stomata per unit of leaf 

 surface varies simultaneously with the length of the pore for the several species, 

 so that two variables are to be considered. No correlation was found between 

 the amount of transpiration and the length of the pore of one stoma or the 

 number of stomata per unit of leaf surface in the different species investigated. 

 No constant relation was found between the amount of water lost and the 

 number of linear units of stomatal pore, that is, the number of stomata per unit 



